Expedition 362: Site U1481

Abstract

Site U1481 (proposed Site SUMA-12A) is located on the Indian oceanic plate, east of the Ninetyeast Ridge, west of the North Sumatran subduction margin, and 35 km southeast of Site U1480. The primary drilling objectives at Site U1481 were (1) To core the deeper interval of the subduction input sedimentary section and basement; (2) To determine if the lower Nicobar Fan, pelagic section, and basement at Site U1480 are representative of this part of the Indian plate; and (3) To understand the degree of heterogeneity of sediment and basement over short distances. Specific objectives for this site include the following: (1) To establish the onset of Nicobar Fan deposition and to determine the primary sources of sediment delivered to the site during early fan history; (2) To identify the principal lithologies that may be involved in development of the plate boundary fault; (3) To establish how the mechanical/strength properties of the different lithologies change with depth to determine trends and the effects of burial rate and burial time; (4) To identify potential discontinuities that may be candidates for décollement positions; (5) To identify any thermal history indicators and any effects of early diagenesis; (6) To identify fluid sources and changes with depth; (7) To determine the composition and origin of basement at the site and its effect on overlying sediments; and (8) To compare the lithostratigraphy, geochemistry, and physical/mechanical properties with those at Site U1480 to establish local variations of the stratigraphic succession.